Spain's anti-austerity Podemos party sought on Sunday to draw a line under a recent internal conflict that has marred its image following its meteoric rise, as supporters voted to back leader Pablo Iglesias and stick to the movement's leftist roots.

Podemos ("We Can") emerged as one of Europe's most prominent anti-austerity parties after winning over millions of voters in the wake of a deep recession and disrupting four decades of a stable two-party system in Spain.

It came third in two inconclusive elections in December 2015 and June 2016 with just over 20 percent of the vote, enough to deny its bigger rivals an absolute majority and putting it almost neck-and-neck with the traditional centre-left Socialists.

But a dispute between some of Podemos' senior leaders over the party's direction barely three years after it was founded by Iglesias and fellow political scientists has threatened to stunt its progress and even raised the prospect of a split.

A majority of grassroots supporters on Sunday rallied behind Iglesias, re-electing him as leader and backing his far-left vision for the party, which was born out of mass street protests at the height of Spain's economic crisis.

Iglesias, a 38-year-old pony-tailed professor who built up a strong personal following through TV talk show appearances, faced a challenge from his number two in Podemos, Inigo Errejon, who has pushed for a more moderate approach with policies designed to lure voters from across the political spectrum.

"Change is still in the air and today Podemos is stronger and more mature," Iglesias told party members at a conference in Madrid after his strategy proposals received the most votes, to chants of "unity, unity".

Errejon, 33, was pushed down the party pecking order as a result of the vote.

Dismay over the spat, which had spilled over into the public arena as Iglesias and Errejon locked horns on Twitter and in parliament, had spread to Podemos' senior ranks and prompted resignations among the leadership team in recent weeks.

Podemos has sought to cast itself as the main opposition party after conservative Prime Minister Mariano Rajoy secured a second term in office last October, at the helm of a minority government.

But many of its supporters are reluctant to see Podemos - which tapped into discontent over political corruption among Spain's old guard - drift ideologically into the centre ground space occupied by the Socialists.

"Podemos needs to reinforce itself on the left," said unemployed Manuel Vidal, 52, at the party conference.

The internal divisions in Podemos come as Rajoy, 61, reinforces his own position and vaunts the stability offered by his party. He was re-elected as leader of his People's Party (PP) on Saturday for the fourth time since 2004.